The present disclosure relates to aircraft environmental control systems. More specifically, the present disclosure relates to a diffuser backing plate of a cabin air compressor for an aircraft environmental control system.
Environmental control systems (ECSs) are utilized on various types of aircraft for several purposes, such as in cooling systems for the aircraft. For example, components of an ECS may be utilized to remove heat from various aircraft lubrication and electrical systems and/or used to condition aircraft cabin air. An ECS includes one or more cabin air compressors which compress air entering the system, from an outside source or from a ram air system. The compressed air is delivered to an environmental control system to bring it to a desired temperature and delivered to the aircraft cabin. After passing through the cabin, the air is typically exhausted to the outside. Cabin air compressors are typically centrifugal compressors comprising an impeller and a diffuser.
During operation, a cabin air compressor causes the pressure at an outlet of the cabin air compressor to be greater than that at an inlet of the cabin air compressor. Several factors affect the performance and efficiency of the cabin air compressor, such as the pressure ratio (the ratio of outlet pressure to inlet pressure for that cabin air compressor), and the mass flow through the cabin air compressor. At relatively high pressure ratios a greater mass flow is required for the cabin air compressor to function stably. If the pressure ratio is too high for the current mass flow the cabin air compressor may start to stall with a loss of even airflow. If the airflow stalls to a sufficient degree the higher pressure at the outlet of the cabin air compressor can cause reverse airflow, which is known as surge.
Surge in a cabin air compressor can result in loss of output and vibration to the cabin air compressor that could possibly damage the cabin air compressor. To avoid surge during operation, the cabin air compressor is designed to have a safety margin between the mass flow and the pressure ratio at which the cabin air compressor will normally be operated, and the mass flow and pressure ratio at which a surge will occur. Expanding the safety margin of the cabin air compressor will increase the operational range of the cabin air compressor.